Investigation of reaction networks and active sites in bio-ethanol steam reforming

over Co-based catalysts

Umit S. Ozkan* (P.I.)I. Ilgaz Soykal

Hua SongXiaoguang Bao

Burcu Mirkelamoglu

Heterogeneous Catalysis Research GroupDepartment of Chemical and Biomolecular Engineering

The Ohio State UniversityColumbus, OH 43210

http://www.che.eng.ohio-state.edu/people/ozkan.html

June 8, 2010*Ozkan.1@osu.edu

2010 DOE Annual Hydrogen Program Review Meeting

Project ID#: DE-FC36-05GO15033PD001

This presentation does not contain any proprietary, confidential, or otherwise restricted information

AcknowledgementUS DOE

OverviewTimeline Start Date - May 1, 2005 End Date - April 31, 2010

(no-cost extension requested) 90% Complete

Budget Total project funding

$1,145,625 (DOE)$299,715 (OSU cost share)

Funding received in FY05$100,000(DOE)$10,458 (OSU Cost share)

Funding received in FY06$185,000 (DOE)$147,987 (OSU cost share)

Funding received in FY07$290,473 (DOE)$67,316 (OSU)

Funding received in FY08$140,703 (DOE)$9,780 (OSU)

Funding received in FY09$429,449 (DOE)$54,163 (OSU)

Funding received in FY10No funding

Barriers A. Fuel Processor Capital Costs C. Operation and Maintenance D. Feedstock Issues

Partners Argonne National Laboratory

Advanced Photon Source Synchrotron techniques

Chemistry Dept. at OSU (Prof. Hadad) Molecular simulation

NexTech Materials, Ltd. Catalyst manufacturing scale-up

Directed Technologies Inc. Economic analysis and feasibility

considerations

PNNL Sharing findings

Project overview Catalytic H2 production from

bioethanol Renewable sources;

Plant matter (natural CO2 recycling);

Lends itself well to distributed H2production strategy;

Non-precious metal catalysts, low-temperature operation

A university program addressing many fundamental questions such as: Catalytic active sites;

Reaction networks and mechanisms;

Surface species and intermediates;

Deactivation mechanisms;

Regeneration mechanisms.

Objectives-Relevance To acquire a fundamental understanding of

the reaction networks and active sites in bio-ethanol steam reforming over Co-based catalysts that would lead to

Development of a precious metal-free catalytic system which would enable Low operation temperature (350-550oC)

High EtOH conversion

High selectivity and yield of hydrogen

High catalyst stability

Minimal byproducts such as acetaldehyde, methane, ethylene, and acetone

Ease of operation

Addressing the barriers Fuel Processor Capital Costs Operation and Maintenance Feedstock Issues

Relevance

ApproachMilestones and Progress

Tasks Progress % comp

1

Setting up the experimental systems, establishing protocols, training

Built, installed a reactor system and established experimental protocols;Completed a HAZOP review for the ethanol reforming reactor system;Went through a safety inspection conducted by a DOE Safety Panel.

100%

2Economic analysis Completed an initial economic analysis based upon a 1,500 kg/day of hydrogen process using

H2A model. 95%

3 Catalyst synthesis and optimization

Prepared over 100 batches of catalysts; Investigated the effect of support, promoters, precursors, active metal loading, synthesis techniques and parameters on catalytic performance.

95%

4In-situ, pre- and post-reaction characterization

Completed characterization studies using CO, N2O and H2 chemisorption, X-ray diffraction, temperature programmed reduction, oxidation, desorption, and thermogravimetric analysis, differential scanning calorimetry.Combined characterization studies (XPS, DRIFTS, LRS, TGA) with mechanistic investigations to understand the pre- and post-reaction nature of the catalyst, reaction mechanisms and deactivation characteristics; XANES and EXAFS studies using the Synchrotron Facilities at Argonne National Laboratories Advanced Photon Source.

90%

5Activity tests, kinetic studies, deactivation, regeneration studies

Established correlations between synthesis parameters, structure and activity;Evaluated synthesized catalysts for ethanol steam reforming in the temperature range 200-500oC and gas hourly space velocities from 5,000-300,000h-1;Conducted transient and steady-state experiments to understand the reaction network and mechanisms; Examined the role of pre-treatment procedures.Initiated studies with dimethyl ether (DME) steam reforming.

90%

6 Information dissemination

Published 12 articles in refereed journals, five articles in conference proceedings, and gave 27 presentations, one key-note lecture and several invited lectures. 90%

7Data analysis, reproducibility tests, literature awareness

Built a literature data base; Data analysis and reproducibility tests are performed in conjunction with the experiments. 90%

Development of non-precious metal,

low-temperature catalysts with:high activity

high selectivityhigh stability

economical feasibilityease of operation

Catalyst formulation

Catalyst characterization

Catalytic testing

Economic analysis

Computational modeling

Technical ApproachAn integrative approach - Iterative with feed-back

Mechanistic studies

Co

Catalytic performance

Technical Accomplishments and ProgressUnderstanding how to control the most important catalytic properties

Pre-treatment/activation parameters

calcination temp., calcination timereduction temp., reduction time

Synthesis methodIWI, SG, CCT

solvothermal, hydrothermal

FormulationLoading, dopants

promoters

Impregnation mediumwater, ethanol

ethylene glycol

Support Morphology3-D ordered macroporous

cubic, cuboid, beltrod, plate, polyhedron

Support effectZrO2, SiO2, Al2O3

CeO2

Precursor effectCo(NO3)2, CoCl2, CoSO4, CoCO3

Co(AcAc)2, CoAc, Co2(CO)8 CoC2O4

Metal DispersionReducibility

Oxygen mobilitySurface acidity

Metal-Support InteractionSupport nano-structure

Activity, Selectivity, Stability

Supported Co3O4crystalline size prepared byCo(AcAc)2: 3-6 nm

Different CeO2nano-structures

Results published in• Catalysis Letters, 132, 422-429 (2009).• J. Molecular Catalysis, 318, 21-29 (2010).• Applied Catalysis A

doi:10.1016/j.apcata.2010.04.01• Green Chemistry, 9, 686-694 (2007). • Journal of Physical Chemistry A. 114, 3796-

3801 (2010).

Technical Accomplishments and ProgressUnderstanding the structural and molecular nature of the catalyst and

the surface sites

Surface area Pore volume

Pore sizePore size distribution

Crystalline phaseParticle size

Molecular structureOxidation state

Coordination environmentWeight variation

Surface energeticsAdsorption/desorption

Reduction/oxidation characteristics

MorphologyParticle size

Elemental analysisSurface intermediates

X-ray photoelectron Spectroscopy

Electron microscopyEDX

ThermogravimetryScanning calorimetry

N2 Physisorption

X-Ray Diffraction

Laser Raman Spectroscopy

Mass Spectrometry

DRIFTS

Adsorptiondesorption

X-ray AbsorptionSpectroscopy

Ethanol steam reformingTemperature programmed reaction

A complex network of reactions catalyzed by different sites

Steady-state reaction experiments

Technical Accomplishments and ProgressUnderstanding the Reaction Network

Results published in Song, H., Zhang, L., Ozkan, U.S., “Reaction Networks in Ethanol Steam Reforming over Supported Co Catalysts,”Industrial and Engineering Chemistry Research, accepted

Transient response experiments

Isotopic labeling experiments

EtOH+D2O TPD

CH3CH2OH →CH3CHO + H2

CH3CH2OH →CH4 +CO + H2

CH3CH2OH →C2H4 + H2OCH3CHO →CH4 +CO

2CH3CHO →CH3COCH3 +CO + H2

CH3CHO + 3H2O → 2CO2 + 5H2

CH3CH2OH + H2O → 2CO +4H2

CH3CH2OH + 2H2O → 2CO2 + 6H2

CO + 3H2 →CH4 + H2OCH4 + 2H2O →CO2 +4H2

CO + H2O →CO2 + H2

CO2 + H2 →CO + H2OC2H4 → coke

CH4 →C + 2H2

2CO →CO2 +C

Technical Accomplishments and ProgressIdentifying the surface species and elucidating the surface mechanisms

Thermogravimetry

Calorimetry

In-situ vibrational spectroscopy

Isotopic labelingMass spectrometry

Temperature-programmeddesorption

Multiple pathways that directly impact the yield, selectivity and stability

Results published in •Song, H. Zhang, L. Watson, R.B., Braden, D., Ozkan, U.S., “Investigation of Bio-ethanol Steam Reforming over Cobalt-based Catalysts,” Catalysis Today, 129, 346-354 (2007).•Song, H. and Ozkan, U.S., “Adsorption/desorption Behavior Ethanol Steam Reforming Reactants and Intermediates over Supported Cobalt Catalysts,” J Phys. Chem. Accepted

Proposed mechanism

Molecular modeling

Technical Accomplishments and ProgressUnderstanding the major deactivation mechanisms

Results published in Song, H., Ozkan, U.S., “Ethanol Steam Reforming over Co-based Catalysts: Role of Oxygen Mobility ,” J. Catalysis, 261 66-74 (2009).Song, H. Ozkan, U.S., :Changing the Oxygen Mobility in Co/Ceria Catalysts by Ca Incorporation: Implications for Ethanol SteamReforming,” Invited paper. Journal of Physical Chemistry A. 114, 3796-3801 (2010).

Primary modes of deactivation

Factors that lead to coking High surface acidity Low oxygen mobility Low metal-support interface

Coking Sintering

Factors that lead to sintering Low dispersion Low oxygen mobility High operating temperatures Need for pre-reduction with H2

Findings from this project that allow us to prevent deactivation Increasing oxygen mobility by creating anion vacancies in the support Neutralizing acidic sites Improving dispersion by using organic ligands in the synthesis Improving activity to reduce the operating temperature Eliminating the need for pre-reduction with H2

Technical Accomplishments and ProgressA catalyst formulation with high activity, selectivity and stability

Over 95% H2 yield No liquid by-products above 300oC Stable activity in accelerated aging study

Co3O4

Co/CeO2 catalyst prepared by a reverse

microemulsion technique

Results published in Song, H., Tan, B. and Ozkan, U.S., “Novel Synthesis Techniques for Preparation of Co/CeO2 as Ethanol Steam Reforming Catalyts,” Catalysis Letters, 132, 422-429 (2009)

CO2

CH3CHOCOCH4Acetone

H2

EtOH:H2O=1:10 (molar ratio);CEtOH=7.5vol.%;

WHSV=~1.08gEtOH/gCat/h;GHSV=~10,000h-1

Technical Accomplishments and ProgressEconomic analysis

Production Cost $/kg

Total Cost (Production/

Storage/Disp.)$/kg

2.75 4.63

Forecourt Production Scale -(1,500 kg H2/day)

Economic analysis based on Aspen Plus and DOE-H2A model. Agreement with Directed Technologies independent analysis. Based on conservative estimates for catalyst life-time and GHSV.

Results published in Song, H. and Ozkan, U.S., “Economic Analysis of Hydrogen Production through a Bio-ethanol Steam Reforming Process: Sensitivity Analyses and Cost Estimations,” International Journal of Hydrogen Energy, 35, 127-134 (2010).

Technical Accomplishments and ProgressUnderstanding the effect of catalyst pre-treatment

hν

X-ray absorption spectroscopy capability wasrecently added

XAFS (X-ray Absorption Fine Structure)spectroscopy provides information on the localatomic structure of a selected element, including:

formal oxidation state coordination bond distances nature of immediate neighbors

Advanced Photon Source (APS) at the ArgonneNational Laboratories was utilized

The APS is a third generation synchrotron facilitywith the nation’s most brilliant X-ray beams

Advanced Photon Source at Argonne National Laboratories

XAFS spectroscopy was utilized to provideinsight on the oxidation state and the localcoordination environment of Co during ethanolsteam reforming with Co/CeO2

New capabilityNew collaboration

New insight

Recent Progress

Technical Accomplishments and ProgressUnderstanding the effect of catalyst pre-treatmentReduction pretreatment

with H2

No pretreatment

Reaction after reduction pretreatment

Cobalt is CoO after reduction pretreatment

Co3O4 over pristine catalyst

Pristine Co/CeO2

After ESR at 350°C

After ESR at 500°C

After ESR at 450°C

After ESR at 350°C

Co3O4 is reduced to CoO during reaction

at 350°C

CoO is further reduced to metallic Co

during reaction

Co reduction takes place under

reaction conditions

CoO is further reduced to metallic Co

during reaction

Recent Progress

Technical Accomplishments and ProgressUnderstanding the effect of catalyst pre-treatment

Rel

ativ

e A

bund

ance

Reduction pretreatment

Co3O4CoOCo

Rel

ativ

e A

bund

ance

No pretreatment

Co3O4CoOCo

XANES Spectroscopy(X-ray Absorption Near Edge)

Reduction pretreatmentis not necessary

for catalytic activity

Ease of Operation

Catalyst reduction takes place under reaction conditions

Both samples converged to the same oxidation state for cobalt regardless of pretreatment

XPS over post ESR samples further supported the conclusion

Recent Progress

Technical Accomplishments and Progress

M-OH3650~3150cm-1, O-H stretching

CH3- or CH3CH2-2962, 2927, 2865 cm-1:C-H stretching1385cm-1: CH3- bending

Monodentate and bidentate ethoxide

1169, 1106, 1063cm-1 CCO stretching

Acetates CH3COO 1569, 1429, 1348cm-1

CO2

2361, 2336cm-1: O=C=O stretching

Molecularly adsorbed H2O1654cm-1

DRIFTS during Temperature-programmed desorption

Thermal transformation of adsorbed species Provides limited information on the surface species during ethanol steam reforming

DRIFTS during ESR Reaction Spectra collected while reaction is progressing Provides information on the surface species and mechanistic steps under true reaction conditions

CH4 (g) CH3CHOVibrational spectroscopy under actual reaction conditions

(operando)

Acetaldehyde formation and decomposition to CH4 and CO2can be directly

observed.

Recent Progress

Technical Accomplishments and Progress

In-situ DRIFTS data show that Co/CeO2catalysts can be used in steam reforming of DMEFormation of various adsorption and oxidation products observed on the surface

Recent Progress

Multi-source clean fuel which can be produced from a wide spectrum of feeds including lignocellulosic biomass

Inert, non-carcinogenic, nonmutagenic, non-corrosive, and virtually non-toxic

Hydrogen content is equal to that of ethanol

Dimethyl ether steam reforming over Co-based catalysts

M-OH3650~3150cm-1, O-H stretching

CH3-2962, 2927, 2865 cm-1:C-H stretching1385cm-1: CH3- bending

Surface Carbonates and methoxy region1176, 1166, 1101, 1079cm-1 v(OC)

CO2

2361, 2336cm-1: O=C=O stretching

Molecularly adsorbed H2O1654cm-1

CH3

OM

Co/CeO2 nanoparticles were found to have high activity as Preferential Oxidation (PROX) catalysts for removing CO from H2streams.

In the 150-180°C, high CO conversion (~100%) and high O2 selectivity to CO2(>90%).

Examined the effect of O2 concentration, H2concentration, space velocity, temperature on conversion and selectivity

Examined possible side reactions (WGS, r-WGS, methanation)

Examined time-on-stream activity

Measured activation energies for CO oxidation and H2 oxidation

Results published in Woods, M. P. Gawade, P., Tan, B. Ozkan, U.S., “Preferential Oxidation of Carbon Monoxide on Co/CeO2 Nano-particles,”Applied Catalysis B: in press. doi:10.1016/j.apcatb.2010.03.015

Nano-particles of CeO2

Technical Accomplishments and ProgressActive and selective catalysts for PROX

Recent Progress

Collaborations

A new collaboration with Argonne National Lab (Dr. Jeffrey Miller and Dr. Christopher Marshall) has been initiated to incorporate XAFS studies in the project. Three consecutive proposals for “In-situ XAFS Characterization of cobalt-based catalysts for steam reforming of bio-derived liquids” have been submitted to Argonne National Laboratory to request beam time at the synchrotron facilities and they all have been accepted. Seven members of the P.I.’s team have registered as facility users at Advanced Photon Source of Argonne National Laboratory. Dr. Miller has been working closely with the team members in in-situ experimentation and data analysis.

Collaboration with Chemistry Department (Prof. Hadad) on combining experimental work with molecular simulation has progressed. A paper, that resulted from this collaboration “Computational Study of the Ethanol Steam Reforming Reaction over Co/CeO2(111): from Ethanol to Acetate” has already been presented at the ACS National Meeting in August 2009. A refereed journal article written jointly has been accepted for publication in Journal of Physical Chemistry. A second collaborative article is in preparation. A post-doctoral researcher and a graduate student are being jointly advised by the P.I. and Dr. Hadad.

Collaboration with Nextech Materials, Inc. for scale-up of the catalyst manufacturing process is in place. A joint proposal (OSU and NexTech) to NSF has been accepted.

Collaboration with PNNL. Sharing findings

Directed Technologies, Inc. Economic analysis and feasibility considerations

SummaryRelevance:A fundamental study aimed at developing precious-metal free catalysts for hydrogen production from bio-ethanol and other bio-derived liquids

Approach:An integrative approach that combines catalyst synthesis, characterization, kinetic studies and molecular simulation in an iterative manner to develop a fundamental understanding of the nature of active sites, reaction networks and reaction mechanisms involved in ethanol steam reforming over Co-based catalysts

Technical accomplishments and progress:Developed an understanding of the reaction networks and surface mechanisms that allow correlating specific sites with specific reaction steps and deactivation mechanisms

Developed techniques for tailoring the catalytic properties to meet the needs of the reaction

Developed promising catalyst formulations that can achieve high H2 yields, high selectivities and high stability at low temperatures

Collaborations:New partnership with Argonne National Lab for XAFS studies

Active partnership with Chemistry Department on molecular simulation

Partnership with NexTech for catalyst manufacturing

Partnership with PNNL and Directed Technologies, Inc. for sharing findings

Proposed Future work:Long term stability tests, accelerated deactivation tests, kinetic measurements to obtain kinetic parameters and allow kinetic modeling, in-situ XAFS studies

Future Work

Kinetic and mechanistic studies will be continued in conjunction with catalystcharacterization under reaction conditions to obtain kinetic parameters. Rate expressionswill be developed for kinetic modeling.

Long term time-on-stream experiments will be continued.

Accelerated deactivation and regeneration studies (e.g., higher C/S ratio and GHSV) will be continued.

Economic analysis will be fine-tuned based on process modification with no pre-reduction.

Molecular simulation work using DFT calculations will be continued and used to guide rational catalyst design. This is a collaborative activity.

In-situ XAFS experiments will be performed at Argonne National Lab to elucidate the oxidation state and coordination environment of cobalt sites during reaction. Accelerated deactivation studies will be coupled with in-situ XAFS studies. This will be a collaborative activity.

Catalyst synthesis for best performing catalysts will be scaled-up through industrial partnership. This is a collaborative activity.

Several more publications are in preparation and will be submitted within the next 6 months.